114. Flatten Binary Tree to Linked List(unsolved)

Given a binary tree, flatten it to a linked list in-place.

For example,
Given

     1    / \   2   5  / \   \ 3   4   6

The flattened tree should look like:
1
\
2
\
3
\
4
\
5
\
6

解答：这道题其实思路比较简单，但是可能编程上要考虑很多意外情况。
简单来说，就是把左子节点中最靠右的叶子节点指向右子节点，然后把整个左子节点挪到右边。然后root往右子节点走一步。如此递归下去。

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    void change(TreeNode* root)    {        while(root)        {           if(root->left&&root->right)             {               TreeNode* t=root->left;               while(t->right!=NULL)               {                   t=t->right;               }               t->right=root->right;           }           if(root->left)               root->right=root->left;           root->left=NULL;           root=root->right;        }    }    void flatten(TreeNode* root) {           change(root);    }};